Rotary drum mixing devices for use in the blending of powdered solids and the blending of solid-liquid mixtures such as concrete and cement are extremely old in the art. Characteristically, such devices have embodied rotatable drums having a relatively small open end, a relatively small closed end and enlarged diameter mid-section. Such drums are rotatably mounted on an axis which is angularly disposed to elevate the open end to thereby provide an enlarged reservoir below such open end for retention of materials being mixed. Such drums are generally provided with a plurality of axially and inwardly extending ribs for lifting portions of the drum contents to speed the mixing operation during rotary movement of the drum. In order to maximize the capacity of such reservoir the drums are frequently fashioned in essentially pear-shaped contour with the maximum diameter being somewhat closer to the closed end of the drum; although in larger drums such as the truck mounted drums used for delivering concrete in the construction industry it is common to have the maximum drum diameter approximately midway between the open and closed ends.
Mixing drums of the type described above generally have been fashioned from steel or other metal for strength and durability, but such drums present a number of problems in production, storage and handling. As unitary bodies of fabricated metal such drums are both heavy and bulky presenting a storage and handling problem from the time of production of the drum until the time of assembling the drum in a mixing apparatus. In addition, such metal drums, when used for mixing cement and concrete require special attention and prompt cleaning after each use to prevent a build-up of hardened cement on the metal surfaces. Cement, as it hardens, bonds tenaciously to most metals and the removal of hardened cement from metal drums is a tedious and time-consuming operation.